China celebrated its Space Day this year on Monday with a series of activities and events. As part of the festivities, the country released global color images of Mars obtained from its first Mars exploration mission.

A launch ceremony of the Space Day was held Monday in Hefei, capital city of east China's Anhui Province, with this year's theme of "Investigate things to extend knowledge, exploring the firmament."

Three people were appointed as image ambassadors for this year's Space Day, including taikonaut Chen Dong, Wang Chi, director of the National Space Science Center under the Chinese Academy of Sciences, and Han Zaifen, a famous artist of Huangmei Opera.

International scientific research cooperation for samples retrieved from the moon by China's Chang'e-5 mission was also announced at the launch ceremony.

About 1,200 guests from over 40 countries are invited to participate in this year's Space Day of China, which includes a series of activities such as the China Space Conference, the International Deep Space Exploration Conference, and the China Space Culture and Art Forum.

Over 400 other activities, including science popularization lectures, space knowledge competitions, and relevant seminars will be held nationwide, according to the China National Space Administration.

Starting in 2016, China designated April 24 as the Space Day of China to mark the launch of its first satellite "Dongfanghong-1" into space on April 24, 1970.